Turning over new leaf in climate change

TAKING THE HEAT / SECOND IN AN OCCASIONAL SERIES Artificial photosynthesis has big upside, challenges

Updated 11:29 pm, Saturday, January 12, 2013

Photo: Mike Kepka, The Chronicle

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Kenny Lee, a mechanical engineer at the Joint Center for Artificial Photosynthesis holds a prototype of an artificial photosynthesis panel on Wednesday January 9, 2012 in Berkeley, Calif. JCAP has entered a race to create earth friendly fuels that some day may actual combat the effects of global warming.

Kenny Lee, a mechanical engineer at the Joint Center for Artificial Photosynthesis holds a prototype of an artificial photosynthesis panel on Wednesday January 9, 2012 in Berkeley, Calif. JCAP has entered a

Mechanical engineer Kenny Lee works on a more efficient way to produce hydrogen at the Joint Center for Artificial Photosynthesis lab in Berkeley.

Mechanical engineer Kenny Lee works on a more efficient way to produce hydrogen at the Joint Center for Artificial Photosynthesis lab in Berkeley.

Photo: Mike Kepka, The Chronicle

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Kenny Lee, a mechanical engineer at the Joint Center for Artificial Photosynthesis produces hydrogen bubbles using a piece of platinum wire and and electric charge on Wednesday January 9, 2012 in Berkeley, Calif. JCAP has entered a race to create earth friendly fuels that some day may actual combat the effects of global warming.

Kenny Lee, a mechanical engineer at the Joint Center for Artificial Photosynthesis produces hydrogen bubbles using a piece of platinum wire and and electric charge on Wednesday January 9, 2012 in Berkeley,

In a tidy white lab on the southern edge of Berkeley, scientists are trying to duplicate one of nature's greatest tricks, pulling energy out of thin air.

They're designing artificial leaves that can convert sunlight, carbon dioxide and water into chemical fuel, much like the photosynthesis of flowers and trees.

The team has already built a crude prototype from silicon, polymers and platinum that can create a simple and clean hydrogen fuel. If the scientists figure out how to cheaply produce more complicated energy sources, it would enable mass production of "drop-in" fuels that could power automobiles, trucks, planes and ships without pumping more greenhouse gas into the atmosphere.

In other words, it could provide a viable alternative to digging up more petroleum, coal and other traditional energy sources widely blamed for global warming.

That simple, that hard

Without drastic changes to global energy systems, studies show that rising fossil fuel emissions could push global temperatures up as much as 3 degrees Celsius by 2050 and 6 degrees Celsius by 2100, unleashing a series of dangerous ecological consequences.

Researchers are investigating an array of possibilities for preventing or offsetting certain effects of a warming world, from sucking carbon out of the atmosphere to increasing the reflectivity of clouds. But even those exploring such options say the only way to address the full scale of global warming is to attack the root cause: cutting greenhouse gas emissions as much and as quickly as possible.

Venture capitalists, startups, corporations, government researchers and academic labs around the region are working aggressively to develop or deploy more efficient renewable energy sources, including next-generation batteries, electric cars, light bulbs, biofuels, hydroelectricity, and geothermal and wind power.

Tapping sunlight

But among clean energy options, tapping into the direct power of sunlight is uniquely promising. The sun casts more energy on the globe in one hour than all of humankind consumes in a year. The problem is that existing technology doesn't efficiently capture and store those diffuse and intermittent beams.

That's where artificial photosynthesis comes in.

It could retain more of the sun's energy than biofuels, which for a variety of reasons store well below 1 percent of the energy in the sunlight that touches them. And unlike solar panels, the energy produced by artificial photosynthesis would be highly portable, packed into a dense fuel that could power vehicles over long distances.

"There are lots of ways to provide electricity to things that don't need to take their energy source with them," said Graham Fleming, vice chancellor for research at UC Berkeley and a chemistry professor who has done groundbreaking research in photosynthesis. "But planes, ships, cars and trucks are a different problem and one we don't have a good solution for."

And it's a big problem. Transportation contributes more than a quarter of total U.S. greenhouse gas emissions, and accounted for nearly half of the net increase during the past two decades, according to the Environmental Protection Agency.

The real challenge

During a tour of the Berkeley lab last month, Frei, a slight Swiss chemist with a head of gray hair, stopped at a work space and picked up the closest thing his team has to an artificial leaf.

The "engineering model" looks nothing like its natural counterpart. Four tilted purple strips fill the translucent box, which fits in the palm of his hand.

It would take a microscope to see that these thin strips are, in fact, tiny fibers made from silicon-based material. They absorb light to power a series of chemical reactions.

Iridium oxide catalysts attached to the tops of the strips split water into oxygen and protons. A membrane in the middle holds back the oxygen, but allows the protons to pass through. Finally, platinum catalysts on the other side of the strips convert the protons to hydrogen (H2), a simple energy carrier.

A convergence of technological and scientific advances has propelled the research to this point. Big strides in computer speeds and software capabilities have accelerated the ability to identify ideal materials. The birth of nanotechnology has allowed scientists to work at the necessary scale of atoms and molecules. And earlier work by Frei and others has enabled humans to capture energy from a larger portion of the sunlight spectrum (see related story).

But there's a major obstacle remaining: The device that Frei displayed isn't anywhere near economical. The components are too expensive and fragile, and the resulting fuel too inefficient.

"That's the real challenge JCAP is trying to take on - not how to do it, but how to do it with cheap, abundant materials," UC's Fleming said.

The other trick is to adapt the process to produce fuels with higher energy density, closer in kind to gasoline, yet renewable.

Such fuels would emit carbon dioxide. But since they would be made from the carbon dioxide already in the air, rather than extracted from the ground, the fuels would be carbon neutral - potentially providing a way to halt the rise of fossil fuel emissions.

The approach was promising enough to catch the eye of the federal government.

Joint project born

In late 2009, the U.S. Department of Energy announced plans to invest $122 million over five years into three "high risk, high reward" energy research projects, including an effort to produce fuel directly from sunlight. The goal was to drive scientific breakthroughs in promising research areas too costly or unproven for the energy industry to take on itself.

"Given the urgency of our challenges in both energy and climate, we need to do everything we can to mobilize our nation's scientific and technological talent to accelerate the pace of innovation," Energy Secretary Steven Chu said at the time.

Envisioning 'forests'

JCAP's researchers would leave the commercialization of the technology they are developing to others, but the ultimate idea is to cover millions of acres of land with artificial leaves. They probably would be made of a polymer-like material roughly an inch thick that could be rolled out like a blanket.

A key advantage over biofuels is that artificial leaves could be installed on nonarable land, reserving limited fertile acres for food production.

If man-made leaves covering 60 million acres converted just 1 percent of the energy in the sunlight that touches them into energy in the resulting fuel, Frei estimates they could produce all the energy now consumed by U.S. transportation. At 7 percent efficiency, they could produce all the energy used in the nation each year.

To be sure, 60 million acres is a lot of land, roughly the size of Oregon. But as Frei points out, there are more than 40 million acres of land devoted to the nation's interstate highways.

His analogy is a deliberate one. It's the space the country dedicated to an earlier national priority - transportation - that has contributed heavily to the problem at hand.

Another comparison: The nation leased more than 38 million acres of federal property to oil and gas companies at the end of fiscal year 2011, according to the latest data available from the Bureau of Land Management, and well above 60 million acres as recently as 1990.

"What it says is that society has already given away that kind of land, so it means it might be a socially acceptable level," Frei said.

High hurdles

"I would not be surprised to learn that one day this will be done on a practical scale, at a reasonable cost," said Sally Benson, director of the Global Climate and Energy Project at Stanford University. "But we are very far from that point."

"When the needed scientific breakthroughs take place is anyone's guess," she said. "And once this occurs, if we can learn from experience in the energy sector, it will be decades before it grows to sufficient scale to displace the alternatives available today."

Opposition, expenses

Indeed, high hurdles have cluttered the path even to proven sustainable energy systems, including political opposition, climate-change denial, human inertia and enormous economic disincentives.

As environmental writer and activist Bill McKibben stressed in a recent Rolling Stone article, there are 2,795 gigatons of carbon in the proven coal, oil and gas reserves of fossil fuel companies. That's five times more than climate scientists say the world could burn with some hope of staying below a 2-degree-Celsius rise in average temperatures, the threshold widely viewed as a dangerous tipping point for the globe.

But research firm Capital Institute estimates those reserves are worth about $27 trillion. They're the primary asset justifying the multibillion-dollar market caps of energy giants. Those companies' stock prices reflect the clear assumption that these fossil fuels will be pulled out of the Earth, whatever the environmental cost.

A growing chorus of experts argues the only way to correct for this economic "externality" - a real cost that isn't accounted for in actual prices - is for government to step in with aggressive public policy, including incentives and penalties to move companies, researchers and citizens in the right direction.

"We need to leave that fossil fuel in the ground, and the only way that will happen is if they're honestly priced," James Hansen, head of NASA's Goddard Institute for Space Studies, said in an address at the Commonwealth Club in San Francisco last month. "Right now, they're heavily subsidized by you, the public."

But even if officials manage to enact effective policies, the world still faces a serious technical challenge. Studies show that the renewable energy options available to date can't get the world to a sustainable level of greenhouse gas emissions.

In fact, aggressively deploying existing technologies wouldn't be enough for California to reach its own legally mandated goal of making greenhouse gas emissions 80 percent lower than 1990 levels by 2050, according to a 2011 report by the California Council on Science and Technology. Achieving that aim will require "intensive and sustained investment in new technologies," the study concluded.

"You could get about halfway there," said Long, co-chair of the committee that produced the report. "The rest of the reduction will require innovation."

No other choice

That's why efforts like those under way at JCAP, specifically highlighted among possible "breakthrough technologies" in the study, are critical. No one knows yet what proposals ultimately will work. It's only clear that something has to.

For now, Frei and his colleagues are focused on achieving the goal they set when applying for the federal grant: building a working prototype that can produce fuel from the sun 10 times more efficiently than current crops. Year three of the Energy Department's five-year funding program just began.

Frei says he is confident they're on track and hopeful they'll secure additional money to continue refining the technology.

"We have to succeed," he said. "We have no other choice."

About the series

Inside cutting-edge Bay Area research focused on containing climate change.